The present invention relates to a keyless tool chuck, and more particularly relates to an improvement in construction of a chuck for firmly holding a tool such as a drill bit or a driver bit of electric work devices without assistance by a chuck key.
One typical example of such a keyless tool chuck is proposed in Japanese Utility Model Laid-open Sho. 63-189509. The tool chuck of this earlier application includes a chuck body which slidably holds a plurality of clamping jaws in its front center section in a coaxial and oblique arrangement. The jaws are placed in outward screw engagement in their proximal sections with a screw ring inserted over the chuck body and this screw ring is outwardly in screw engagement with an operation sleeve idly inserted over the chuck body for manual operation.
As the operation sleeve is manually rotated, the screw ring is driven into rotation for convergent, collective sliding of the jaws via screw feeding and the collected jaws clamp a tool in position.
With the above-described construction, manual rotation of the operation sleeve is amplified by the screw feeding operation of the screw ring and converted into the convergent, collective sliding of the clamping jaws. This mechanism, however, cannot provide the tool chuck with a high degree of clamping force which is equivalent to that exhibited by a key type tool chuck. Its insufficient clamping force tends to allow easy development of play, or to say the least loosening, between the jaws and the tool, thereby making the tool chuck quite unsuited for use under high torque conditions. Further, in use, seizure tends to occur at contact spots between the chuck body and the operation sleeve, thereby seriously hindering smooth manual rotation of the operation ring.